1) Field of the Invention
The present invention relates to a shielding base member and a method of manufacturing the same and, more particularly, a shielding base member for shielding from electromagnetic radiation, etc., that leak out from the PDP (Plasma Display Panel), etc. and a method of manufacturing the same.
2) Description of the Related Art
In recent-years, the applications of the PDP (Plasma Display Panel), which has a wide viewing angle and good display quality and provides a large screen, have broadened quickly into multimedia display devices, etc.
The PDP is a display device that utilizes a gaseous discharge. The gas that is sealed in the tube is excited by using the discharge to generate a line spectrum that has a wide wavelength range extending from the ultraviolet range to the near-infrared range. A fluorescent substance is arranged in the tube of the PDP. This fluorescent substance is excited by the line spectrum in the ultraviolet range to generate light in the visible range. A part of the line spectrum in the near-infrared range is emitted from the surface glass of the PDP to the outside of the tube.
The wavelength in this near-infrared range is close to the wavelength (800 nm to 1000 nm) that is employed in a remote control unit, optical communication, etc. If these devices are operated near the PDP, it is possible that a malfunction may be caused and therefore leakage of the near-infrared ray from the PDP must be prevented.
Also, the electromagnetic radiation such as microwave, ultra low frequency radiation, etc., are generated by the operation of the PDP, and then leak out to the outside, although amount of the leakage is very small. Since the provisions for leakage of electromagnetic radiation, etc., are specified in the information device or equipment, or the like, the leakage of the electromagnetic waves must be suppressed below the specified value.
In addition, when rays of light are incident upon the display screen from the outside, the incident light is reflected by the display screen and also the contrast ratio of the screen is lowered since the display screen of the PDP is flat. Therefore, the reflection of the incident light from the outside must be suppressed.
For the purpose of satisfying these requirements, a shielding base member is arranged in front of the display screen of the PDP.
In the related art, such a shielding base member is manufactured by the method in which a plastic film to which a metal foil is adhered is pasted on the transparent glass substrate and then the metal foil is patterned, or the like. More particularly, normally the thickness of the metal foil is thin, such as about 10 μm. Therefore, in order to make the handling of the metal foil easy, first the metal foil is pasted onto the plastic film. Then, in order to pattern the metal foil with good precision, the plastic film having the metal foil thereon is pasted on the glass substrate that has strong rigidity, and then the metal foil is patterned.
In the related art, because the metal foil and the plastic film are formed integrally to make the handling of the metal foil easy, if the shielding base member is manufactured using same, the plastic film remains on the shielding base member. The plastic film has low optical transmittance and high haze (degree of opaqueness), as compared with the transparent glass substrate.
Accordingly, since the plastic film remains on the shielding base member, the optical transmittance of the shielding base member is lowered and the haze (degree of opaqueness) the shielding base member is increased. As a result, there is the problem of poorer visibility of the screen of the PDP due to the shielding base member.
In order to further increase the rigidity of the plastic film on which the metal foil is pasted, there is the shielding base member in which the metal foil is pasted onto the plastic film via an adhesive layer. In the case that the plastic film is rolled up on a roller in manufacture utilizing the roll-to-roll method, etc., if the adhesive layer is pressed by foreign matter, etc., dents are readily formed occurs in the adhesive layer because the adhesive layer is soft in itself and the quality of the shielding base member is lowered.
In other related art, the shielding base member includes a plastic film having a near-infrared absorbing function. Thus, the structure of such shielding base member becomes complicated and also incorporates the plastic film. As a result, there remain the problems that the optical transmittance of the shielding base member is further lowered and that the haze (degree of opaque) is further increased.